Delivering targeted color light through a multimode fiber by field synthesis

Recent developments of wavefront shaping make the multimode fiber (MMF) as a promising tool to deliver images in endoscopy. However, previous studies using the MMF were limited to monochromatic light or polychromatic light with narrow bandwidth. The desires for colored imaging stimulate us to deliver multi-wavelength light that covers the entire visible spectrum through the MMF. In this work, we demonstrated delivering targeted color light through the MMF by mixing three primary colors (red, green, and blue) with a single spatial light modulator. The optimum phase map that considers all three colors was generated through field synthesis (FS), which requires every pixel of the SLM to partially account for all colors. With both theoretical and numerical approaches, we showed that FS exhibited much better performance than the previously developed spatial segmentation method that employs different pixels to represent different colors. Moreover, by computationally adjusting the compositions of the weight for each color, the colors of the delivered focus can be switched at video framerate. We anticipate that our work paves a way for future applications of delivering color images through the MMF in endoscopy. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.